Snow Could Affect Grapevine As Rain, Cool Temperatures In Santa Clarita Weather Forecast Cooler temperatures and rain are in the Santa Clarita weather forecast for the next week, bringing snow levels down to elevations that could affect the Grapevine. Starting Friday the first of three storms is expected to arrive in Santa Clarita, said Rich Thompson, a meteorologist with the National Weather Service. “The first chance of rain will be beginning (Friday) afternoon through Sunday morning, with the best chance of rain during the day Saturday,” Thompson said. The first storm is expected to bring light scattered showers, bringing at most one-quarter inch of rain, according to officials.